Instrumented Plate for Oven

The invention relates to an instrumented plate intended for the monitoring of a refractory part of a furnace, in particular a metallurgical or glass furnace, notably for determining an appropriate time to repair or stop the furnace.

The invention also relates to a furnace comprising a refractory part subjected to high temperatures and such an instrumented plate disposed to monitor said refractory part, in particular evaluate the thickness, the mean temperature, or a state of damage of said refractory part.

In general, “furnace” refers to an installation or a reactor comprising a chamber and a heating system designed to establish a temperature of above 800° C. in said chamber.

A furnace is in particular used for the fabrication of fused products, for example for the fabrication of metallurgical or glass products, but also for the incineration of waste or the generation of energy from fuels. For example, a reaction gas turbine is considered to be a furnace.

A furnace can consume gas or other fuels, or be provided with electrical resistances, or be heated by induction.

A metallurgical furnace may be an installation in which a metal precursor is reduced in order to obtain cast iron. A metallurgical furnace may also be a metal smelting furnace or a remelting furnace. For example, a furnace may be a blast furnace for smelting cast iron from iron ore or for remelting copper cathodes smelted by another process, for example for producing copper wire.

A glass furnace can be an installation in which a vitrifiable mixture, in particular comprising oxides, carbonates, sulfates and nitrates, is melted and refined.

The walls of the chamber of a furnace are conventionally protected with a refractory lining. The refractory lining undergoes different chemical and mechanical stresses depending on the application. Its composition is adapted as a result. For example, the interior of a glass furnace is conventionally subjected to a temperature of approximately 1500° C. The refractory lining in contact with the molten glass should moreover resist abrasion by the molten glass.

The composition of the refractory lining is in particular adapted to the targeted application.

For example, the refractory lining in contact with the molten glass or with its vapors is conventionally made of a refractory product of the alumina-zirconia-silica (AZS for short) type generally containing from 30% to 45% by weight of zirconia, a product with a very high zirconia content (typically more than 85% by weight of zirconia), a product with a high alumina content (typically more than 90% by weight of alumina), or a zircon product, or a chromium oxide product.

In a copper cathode melting furnace, the refractory lining is generally based on SiC.

In a blast furnace for cast iron, refractory linings made of SiC, corundum, SiAION, carbon or mullite are conventionally used, depending on the area in question of the furnace.

In order to optimize the service life of the refractory lining, measurements can be taken on the inside or outside of the furnace. These measurements make it possible to plan repair operations, notably hot-repair operations, or refractory lining replacement operations with greater precision.

For example, temperatures can be read off by infrared thermography, but this is possible only at locations that are visually accessible by an infrared camera, this excluding notably certain parts of the lining of the furnace. Furthermore, this solution generally does not allow continuous monitoring.

Measuring devices permitting continuous monitoring in a nonintrusive way, that is to say without entering the chamber of the furnace, are known. Notably, WO2020025492A1 describes, to measure the wear of a refractory lining for a glass furnace, the use of a network of optical fibers sandwiched between the cold face of the blocks of the side wall of the tank of the furnace and a thermally insulating layer, or through said insulating layer. Moreover, EP1527306A1 describes, to measure the temperature in a metallurgical induction furnace, the use of an optical fiber disposed within a fibrous mat between a dense refractory lining and an inductor insulator.

The solutions of the prior art allowing continuous monitoring do, however, pose problems

There is therefore a permanent need for a solution which is easy to implement (installation, maintenance) and makes it possible to monitor the refractory lining of a furnace continuously and reliably, without considerably modifying the behavior of the furnace, and in particular without modifying the thermomechanical stresses exerted on the refractory lining or disrupting the transfers of heat through the refractory lining.

An aim of the invention is to meet this need, at least partially.

The invention relates to an instrumented plate intended for the monitoring of a refractory part of a furnace, and in particular a refractory part having a hot face subjected to a temperature above 800° C., or even above 1000° C., above 1200° C., above 1400° C. or above 1500° C., the instrumented plate comprising:

As will be seen in more detail in the rest of the description, the inventors have discovered that a plate made of a ceramic-matrix composite constitutes a sensor support that is particularly well suited to the targeted applications. A ceramic-matrix composite has good resistance to high temperatures and effectively protects the sensor, notably from mechanical impacts. It is easy to manipulate and install.

Furthermore, the inventors have discovered that the presence of orifices limits interactions with the refractory part. In particular, the presence of the instrumented plate on the refractory part does not substantially provide any additional mechanical stresses or thermal insulation. The furnace therefore does not have to be modified because of the installation of the instrumented plate, notably when the face of the refractory part on which the instrumented plate is immobilized is cooled, for example by blowing air.

Moreover, the inventors have discovered that the presence of orifices significantly reduces the transmission of mechanical stresses to the sensor. The reliability is therefore improved.

Lastly, the instrumented plate can be shaped to fit this face of the refractory part, thereby improving the accuracy of the measurements taken.

The instrumented plate may also comprise, notably, one or more of the following optional and preferred features:

The invention also relates to a measuring device comprising an instrumented plate according to the invention and a measuring appliance communicating with the sensor so as to receive and interpret a signal emitted by the sensor.

Preferably, the measuring device uses the signal it receives from the sensor to provide information relating to:

Those skilled in the art know to select sensors that are suitable for the desired information.

The invention also relates to a furnace comprising a measuring device according to the invention.

The furnace may also comprise, notably, one or more of the following optional and preferred features:

A “refractory part” is understood to mean an element of the furnace made of a refractory material. A refractory part may be a block, but also an assembly of blocks, for example a side wall of a tank, or a floor, notably formed by casting. A refractory part is conventionally made of a fused material or a sintered material. Conventionally, an insulating layer covers the cold face of the refractory part in order to limit exchanges of heat. The insulating layer may be absent, for example in a part of the refractory lining of an incineration furnace or in a blast furnace.

Conventionally, when the refractory part has a hot face, its “thickness” is its dimension measured in a direction perpendicular to its hot face. For example, for a tank side block in contact with molten glass or metal, the thickness is measured in a substantially horizontal direction toward the bath of molten glass or metal. For a floor, the thickness is measured in a vertical direction.

The “hot face” is that face of a refractory part that is exposed to a space of the furnace which is at above 800° C., for example containing molten glass or metal or intended to contain molten glass or metal. The hot face may be in contact, or intended to be in contact, with molten glass or metal and/or with the gaseous environment that extends above the molten glass or metal. The hot face is thus that face of the refractory part that is subjected or is intended to be subjected to the highest temperatures. All of the hot faces of the blocks of the side wall of the glass or metal melting tank may together also, by extension, be described as a “hot face”. The upper surface of the floor may also be described as a “hot face.”

The adjective “hot” is used for the sake of clarity. Before the furnace is in service, the “hot” face is the face which is intended to be subjected to the highest temperatures after being put into service.

A “cold face” is a surface area of the refractory part that is not exposed to a space of the furnace which is heated to above 800° C., that is to say which is insulated from this space by the material of the refractory part. The cold face opposite the hot face is the face which is furthest from said space. Conventionally, the cold face opposite the hot face is the face which, in service, is subjected or which is intended to be subjected to the lowest temperatures. The cold face may be parallel to the hot face.

The “use position” is the configuration in which the instrumented plate rests on a face, for example the cold face, of the refractory part so as to acquire a measurement relating to said refractory part.

The term “plate” conventionally denotes a component having two large faces that are substantially parallel to one another and having a small thickness with respect to the surface area of a said large face, the thickness direction of the plate being perpendicular to said large faces. The “maximum thickness/surface area of the large face” ratio is preferably less than 1/500 m, preferably less than 1/1000 m, preferably less than 1/5000 m, and preferably less than 1/10000 m.

The “surface area” of a plate is the area inside the perimeter of the plate. The surface area of the plate therefore includes the surface area defined by the material of the plate and the surface area of the orifices passing through the plate.

The thickness of the instrumented plate is its dimension measured perpendicularly to the large face of the instrumented plate intended to be positioned or positioned against the refractory part.

An orifice passing through a plate is an orifice which has first and second openings leading into the first and second large faces of the plate. An orifice is preferably rectilinear and preferably extends perpendicularly to the large faces of the plate. The “surface area” of an orifice is the surface area of its opening on the side of the refractory part against which the plate is intended to be placed. The length of an orifice is the largest dimension of this opening. Its width is the largest dimension of this opening perpendicularly to the direction of its length.

A “perforated surface area” is understood to mean the cumulative surface area of all of the surface areas of the orifices.

The percentage of perforation of a perforated zone (or of the instrumented plate) is the ratio of the perforated surface area of said perforated zone (or of said instrumented plate, respectively) to the surface area of said perforated zone (or of said instrumented plate, respectively) which includes said perforated surface area.

The “equivalent diameter” of an orifice is the diameter of a disk having the same surface area as this orifice.

A “fused product”, often referred to as “electrofused”, is understood to mean a product obtained by complete solidification of a composition in the liquid state obtained by melting a mixture of appropriate raw materials in an electric arc furnace or by any other suitable technique.

A “sintered product” is understood to mean a product obtained by mixing appropriate raw materials, and then shaping this mixture in the green state and firing the resulting green form at a temperature and for a time that are sufficient to sinter this green form, it being possible to perform said firing in situ during use.

A “ceramic-matrix composite”, or “CMC”, is conventionally understood to mean a product composed of fibers interlinked by a ceramic matrix. The fibers will be selected depending on the environment in which the ceramic-matrix composite is to be placed, notably depending on the conditions regarding temperature, corrosion, thermal cycling, expansion, and according to the nature of the refractory part that is to be furnished.

The arrangement of the fibers, which constitutes the fibrous support for the matrix, is selected depending on the desired shape for the ceramic-matrix composite, and on the ease with which the sensor can be attached to it. For example, a stack of woven fabrics or insulating mats is well suited to simple plates, a filament winding is well suited to plates having a geometry that exhibits symmetry of revolution, and filament placement is well suited for complex shapes of large dimensions.

A “ceramic-matrix composite precursor” is a material which is capable of transforming into said ceramic-matrix composite under the effect of heating, preferably to above 600° C., preferably to above 700° C., preferably under the effect of sintering.

The fibers are conventionally in the form of a textile. The CMC may then be described as “ceramic-matrix textile”.

A textile may be:

A textile is distinguished in particular from a fibrous mat, in which the organization of the fibers or yarns is random in the three spatial dimensions.